fizzbuzz.hs

import System.Environment

fizzbuzz n 
    | 0 >= n = error "n must be >0."
    | otherwise =
        let fb x
                | 0 == mod x 15 = "FizzBuzz" 
                | 0 == mod x 5  = "Buzz" 
                | 0 == mod x 3  = "Fizz" 
                | otherwise = show x
        in [ fb x | x <- [1..n] ]

main = do
    args <- getArgs
    mapM putStrLn $ fizzbuzz (read (head args) ::Int)

helloworld.hs

main = putStrLn "hello, world."